Characterization of phytoplankton by pigment analysis and the detection of toxic cyanobacteria in reservoirs with aquaculture production

Made available in DSpace on 2018-12-11T17:19:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01The intensified use of water bodies and reservoirs for aquaculture production has increased the need for monitoring and early warning of toxins from cyanobacteria. To minimize effects from toxins, simple and fast analytical monitoring methods are crucial. Here, the content of pigments and microcystins in 14 different strains of cyanobacteria cultured under different growth conditions was investigated to determine the influence of light and nutrient starvation on pigment/ chlorophyll a (chl a) ratios. The obtained pigment/chl a ratios were applied in the software CHEMTAX to calculate the biomass of toxic cyanobacteria, as well as other phytoplankton groups. CHEMTAX ratios from the laboratory cultures were applied to water samples collected during 4 sampling periods at 6 fish farms in different reservoirs in São Paulo State, Brazil. Cyanobacteria generally dominated in all reservoirs in all sampling periods and constituted on average 44 to 66% of the average phytoplankton biomass. The concentrations of microcystins were significantly correlated with the chl a concentrations of cyanobacteria and showed that the pigment method can be used to detect microcystin-producing cyanobacteria in these Brazilian reservoirs. When the concentration of cyanobacteria in the reservoirs was above 4 μg chl a l-1, microcystins were always detected. Our results show that pigment analysis can be used to provide fast and reliable results for the early warning, the presence and potential risk of toxic cyanobacteria in freshwater reservoirs used for aqua culture.Environment and Toxicology DHISão Paulo State Agribusiness Agency TechnologySection of Microbial Ecology and Biotechnology Department of Plant and Environmental Sciences University of CopenhagenFicology Department Botanical InstituteUNESP Campus Botucatu Institute of Biosciences Parasitology DepartmentUNESP Campus Botucatu Institute of Biosciences Parasitology Departmen

Relations between abundance of potential geosmin- and 2-MIB-producing organisms and concentrations of these compounds in water from three Australian reservoirs

Relationships between the abundance of potential geosmin- and 2-methylisoborneol-producing (2-MIB) cyanobacteria and bacteria, and concentrations of the two taste and odour compounds (T&Os) were examined in a 7 day incubation of natural water from the surface and bottom of three reservoirs in southeast Queensland, Australia. Only a single known T&O-producing cyanobacterium (Geitlerinema spp.) was detected by microscopy at low density, and only in one reservoir. Densities of potential T&O-producing Streptomyces (determined by quantitative polymerase chain reaction (qPCR) assay) were highest in the bottom water and varied from 0.7 × 103 to 775 × 103 cells L−1. Geosmin ranged from 6 to 59 ng L−1 (with the highest concentrations in the bottom water), while 2-MIB varied from 6 to 47 ng L−1 (with the highest concentration in surface water). Concentrations of both compounds declined during the incubation under both light and dark conditions. Presence of the geosmin synthase gene, geoA, in cyanobacteria and Streptomyces was examined by different PCR approaches. Cloning of PCR products from amplification of geoA showed a high similarity to geoA in cyanobacteria, but not to streptomycetes. Our results demonstrate that more research on the ecology and molecular biology of T&O producers is required to better understand the dynamics of T&Os and to monitor emerging T&O episodes.No Full Tex

Case study on depuration of RAS-produced pikeperch (Sander lucioperca) for removal of geosmin and other volatile organic compounds (VOCs) and its impact on sensory quality

Effect of depuration on content of geosmin in pikeperch (Sander lucioperca) produced in a commercial RAS farm was examined during a 15-day period. Concentrations of geosmin in the fish were related to geosmin content in the water. For depuration, half of the water volume in a 230 m3 production tank was replaced daily with geosmin-free water. After 8 days of depuration and absence of feeding, content of geosmin in the fish was reduced from 710 ± 245 ng/kg to 165 ± 50 ng/kg (mean ± SD, p < .01). Additional depuration for 7 days only reduced the geosmin content to 135 ± 24 ng/kg. Geosmin concentration in the water was initially 34 ng/L but declined to 10 ng/L after 15 days. Changes in geosmin concentrations in water of the depuration tank indicated that geosmin was released by the fish during the depuration. In addition to removal of geosmin, the depuration also decreased concentrations of 28 different volatile compounds from the fish. Sensory analysis showed decrease in intensity of geosmin flavor upon depuration and improved the overall sensory quality of the fish after 2 weeks of depuration. Our study shows that geosmin and other off-flavors in pikeperch from RAS production can efficiently be removed to be a level that is below the threshold to most consumers